This document discusses module level concepts in software engineering. It defines a module as a logically separable part of a program. It describes two criteria for producing modular designs: coupling and cohesion. Coupling refers to the degree of interdependence between modules, with the aim being low coupling or loose coupling between modules. Cohesion measures the strength of relationships within a module, with the aim being high cohesion where a module focuses on a single function. The document outlines different types of coupling and cohesion and their definitions.

1. SOFTWARE ENGINEERING
MODULE LEVEL
CONCEPTS

2. Module Level Concepts
A module is a logically separable part of a program.
It is a program unit that is discreet and identifiable with respect to compiling
and loading.
To produce modular designs, some criteria must be used to select modules so
that the modules support well-defined abstractions and are solvable and
modifiable separately.
Often used together, two modularization criteria are:
A. Coupling
B. Cohesion

3. Module Level Concepts
A. Coupling
Its an inter-modular concept.
Coupling is the degree of interdependence between
modules. Tightly coupled modules are strongly
dependent on each other. However, loosely coupled
modules are not dependent on each other.
The aim of partitioning/ modularization is to achieve
lowest degree of coupling i.e. highest level of
abstraction.

4. Module Level Concepts
Types of Coupling
1. No Direct Coupling
There is no direct coupling between two modules.
2. Data Coupling
When data of one module is passed to another module, this is called data coupling.
3. Stamp Coupling
When the module passes entire structure to another module, they are said to be stamp coupled.
4. Control Coupling
Control Coupling exists among two modules if data from one module is used to direct the structure of
instruction execution in another.
5. External Coupling
External Coupling arises when two modules share an externally imposed data format, communication
protocols, or device interface. This is related to communication to external tools and devices.
6. Common Coupling
Two modules are common coupled if they share information through some global data items.
7. Content Coupling:
Content Coupling exists among two modules if they share code, e.g., a branch from one module into another
module.

5. Module Level Concepts
B. Cohesion
Its an intra-modular concept.
Cohesion measures the strength of relationships
between pieces of functionality within a given
module.
The aim of partitioning/ modularization is to achieve
highest degree of cohesion.

6. Module Level Concepts
Types of Cohesion
1. Functional : Functional Cohesion is said to exist if the different elements of a module, cooperate to achieve a single
function.
2. Sequential : A module is said to possess sequential cohesion if the element of a module form the components of
the sequence, where the output from one component of the sequence is input to the next.
3. Communicational : A module is said to have communicational cohesion, if all tasks of the module refer to or update
the same data structure, e.g., the set of functions defined on an array or a stack.
4. Procedural : A module is said to be procedural cohesion if the set of purpose of the module are all parts of a
procedure in which particular sequence of steps has to be carried out for achieving a goal, e.g., the algorithm for
decoding a message.
5. Temporal : When a module includes functions that are associated by the fact that all the methods must be executed
in the same time, the module is said to exhibit temporal cohesion.
6. Logical : A module is said to be logically cohesive if all the elements of the module perform a similar operation. For
example Error handling, data input and data output, etc.
7. Coincidental : A module is said to have coincidental cohesion if it performs a set of tasks that are associated with

7. DIFFERENCES BETWEEN COUPLING AND COHESION
Coupling Cohesion
Coupling is also called Inter-Module Binding. Cohesion is also called Intra-Module Binding.
Coupling shows the relationships between
modules.
Cohesion shows the relationship within the module.
It shows relative independence between the
modules.
It shows the module's relative functional strength.
While creating, you should aim for low coupling,
i.e., dependency among modules should be less.
While creating you should aim for high cohesion,
i.e., a cohesive component/ module focuses on a
single function with little interaction with other
modules of the system.
In coupling, modules are linked to the other
modules.
In cohesion, the module focuses on a single thing.